Lighting and its influence on broiler breeders

The importance of good lighting is being increasingly recognised, and justifiably in our opinion. An optimal light climate has a major influence on broiler breeder welfare and performance.

After rearing, the reproductive life of a broiler breeder is divided into three main phases. The first phase, the sexual maturation phase, lasts from photo stimulation until the first egg is laid. The second phase starts at sexual maturity and ends at peak production. The third and final phase lasts from peak production to the end of lay. The efficiency of production in each of these periods is greatly dependant on several key factors, one of which is light management.

Poultry vision

Poultry eyes are relatively large compared to human eyes. The position of the eyes on the side of the chicken’s head gives them small binocular and wide monocular vision. In general, poultry are neither short sighted nor long sighted. This means they can focus nearby and far away at the same time. In this way they are able to remain cautious while foraging. The visible spectrum of poultry also differs from that of humans. The visible spectrum is species specific: it is perceived differently by each species.

Photoreception

Broiler breeders receive light through the eyes; this affects the photoreceptors in the retina. Light that enters the eyes affects behaviour and internal processes.

In addition, light also passes through the skull, where it affects photoreceptors in the hypothalamus, the pineal gland, the pre-optic area and the lateral septal organ. Light that reaches these ‘deep-brain’ photoreceptors affects the biological processes of broiler breeders.

Light also regulates the biological clock and the pituitary gland, which in turn affect the regulation of growth hormones and the broiler breeders’ metabolism through the thyroid glands.

Fig 1: The way poultry receives light

Photo stimulation

Broiler breeders are still close to nature, which means they are seasonal breeders. Seasonal breeders are hatched in a refractory state (juvenile photorefractoriness). Photorefractoriness is the inability to be responsive to photoperiods or changes in photoperiods. In nature, it prevents broiler breeders from becoming sexually active in their first year of life. This means that the light programme has to be adjusted in a specific way to dissipate this and to properly stimulate them sexually.

It is important to adjust the light programme and intensity during the different life phases of the broiler breeder. Using high light intensities and long photoperiods is highly recommended during the first few days in the new house, either with rearing or production. This enables the chickens to explore their new environment and easily find feed and water. After that, it’s best to slightly decrease the lux levels and photoperiods . Lux levels still have to be kept high to stimulate the birds to move through the house and to prevent floor eggs. In cage housing, this is unnecessary, since the chickens don’t need to be stimulated to move through the house and floor eggs are not an issue.

The different aspects of lighting have various consequences for broiler breeders. The most important aspects are light distribution, light spectrum, dimmability and flicker.

Light distribution

Light distribution is important in every phase of a broiler breeder’s life. During the rearing period, uniform light will ensure uniform growth of the flock. Consequently, when moved to the production house, the chickens will be simultaneously stimulated sexually. This means that their age at the first egg will also be uniform.

In the production phase, different kinds of housing systems have different needs with regard to lighting. This explains the importance of using a customised light plan.

Light spectrum

It is important to use a broad light spectrum in poultry houses. Each colour of the spectrum has its own characteristics and own influences on the chickens’ welfare and performance. In broiler breeder houses, it is crucial to use warm, white light with a broad light spectrum.

Fig 2: Warmwhite LED vs. human & poultry spectrum

Dimmability

100-0%, evenly dimmable lights are a must-have. In nature, sunset and sunrise determine the day and night rhythm of the broiler breeders. When sunset starts, they fill their crops before settling for the night. It is important that the lighting equipment is able to simulate natural sunrise and especially sunset. If sunset is naturally simulated, the broiler breeders can settle more comfortably for the night. If the lights are suddenly switched off, the birds will scare, leading to increased stress.

Flicker

Photometric flicker, or flicker, is the (rapid) change of the light output of a lamp. Flicker is a major source of stress for chickens in general and thus for broiler breeders. It is therefore vital to use 100% flicker-free lighting. Chickens originally lived in the jungle, where they were prey animals. They had to be continuously on their guard. The rapid change in light output of a lamp (flicker) is presumed to give chickens the impression that a predator bird is hovering above them; this is perceived as a potential threat. This potential threat significantly increases stress levels.

Fig 3: Flicker vs. flicker-free lighting

Conclusion

Good lighting is of immense importance in broiler breeder housing. Sexual stimulation, uniformity and stress are just a few of the multiple factors that can be positively influenced by providing an optimal light climate. Make sure you opt for a lighting solution, a light programme and a light plan that meet the specific criteria of the house and the birds in it to increase animal welfare and performance.